This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A182452 #8 Jan 08 2025 17:04:16 %S A182452 1,11,111,1111,2222,11111,12222,21222,22122,22212,22221,111111,112222, %T A182452 121222,122122,122212,122221,211222,212122,212212,212221,221122, %U A182452 221212,221221,222112,222121,222211,222336,222363,222633,223236,223263,223326,223362,223623 %N A182452 Numbers for which the sum of reciprocals of square of digits is an integer. %e A182452 223623 is in the sequence because 1/2^2 + 1/2^2 + 1/3^2 + 1/6^2 + 1/2^2 + 1/3^2 = 1 is an integer. %p A182452 T:=array(1..10):for n from 1 to 10^7 do:T:=convert(n,base,10):n1:=nops(T): s:=0:j:=0:for k from 1 to n1 do:if T[k]<>0 then s:=s+evalf(1/T[k]^2):else j:=1:fi: od: if j=0 and s=floor(s) then printf(`%d, `,n):else fi:od: %t A182452 f[ n_ ] := 1/n^2; a[ n_ ] := Apply[ Plus, Map[ f, IntegerDigits[ n ] ] ] ; Select[ Range[ 1000 ], FreeQ[ IntegerDigits[ # ], 0 ] && IntegerQ[ a [ # ] ] & ] %Y A182452 Cf. A034708. %K A182452 nonn,base %O A182452 1,2 %A A182452 _Michel Lagneau_, Apr 29 2012